Fix DynamicExpressionParser and ExpressionPromoter to support LambdExpression (#649)

* Fix DynamicExpressionParser and ExpressionPromoter to support LambdaExpression

* ut

Author: StefH

src/System.Linq.Dynamic.Core/DynamicExpressionParser.cs

@@ -120,24 +120,24 @@ public static LambdaExpression ParseLambda(Type? delegateType, ParsingConfig? pa
 
             var parsedExpression = parser.Parse(resultType, createParameterCtor);
 
-            LambdaExpression lambdaExpression;
+            if (parsedExpression is LambdaExpression lambdaExpression)
+            {
+                return lambdaExpression;
+            }
+
             if (parsingConfig is { RenameParameterExpression: true } && parameters.Length == 1)
             {
                 var renamer = new ParameterExpressionRenamer(parser.LastLambdaItName);
-                parsedExpression = renamer.Rename(parsedExpression, out ParameterExpression newParameterExpression);
+                parsedExpression = renamer.Rename(parsedExpression, out var newParameterExpression);
 
-                lambdaExpression = delegateType == null ?
+                return delegateType == null ?
                     Expression.Lambda(parsedExpression, newParameterExpression) :
                     Expression.Lambda(delegateType, parsedExpression, newParameterExpression);
             }
-            else
-            {
-                lambdaExpression = delegateType == null ?
-                    Expression.Lambda(parsedExpression, parameters) :
-                    Expression.Lambda(delegateType, parsedExpression, parameters);
-            }
 
-            return lambdaExpression;
+            return delegateType == null ?
+                Expression.Lambda(parsedExpression, parameters) :
+                Expression.Lambda(delegateType, parsedExpression, parameters);
         }
 
         /// <summary>

src/System.Linq.Dynamic.Core/Parser/ExpressionPromoter.cs

@@ -22,7 +22,17 @@ public ExpressionPromoter(ParsingConfig config)
         /// <inheritdoc />
         public virtual Expression? Promote(Expression expr, Type type, bool exact, bool convertExpr)
         {
-            if (expr.Type == type || type.IsGenericParameter)
+            Type returnType;
+            if (expr is LambdaExpression lambdaExpression)
+            {
+                returnType = lambdaExpression.GetReturnType();
+            }
+            else
+            {
+                returnType = expr.Type;
+            }
+
+            if (returnType == type || type.IsGenericParameter)
             {
                 return expr;
             }
@@ -103,7 +113,7 @@ public ExpressionPromoter(ParsingConfig config)
                 }
             }
 
-            if (TypeHelper.IsCompatibleWith(expr.Type, type))
+            if (TypeHelper.IsCompatibleWith(returnType, type))
             {
                 if (type == typeof(decimal) && TypeHelper.IsEnumType(expr.Type))
                 {

test/System.Linq.Dynamic.Core.Tests/DynamicExpressionParserTests.cs

@@ -580,7 +580,7 @@ public void DynamicExpressionParser_ParseLambda_Select_2()
 
         // https://github.com/StefH/System.Linq.Dynamic.Core/issues/58
         [Fact]
-        public void DynamicExpressionParser_ParseLambda_4_Issue58()
+        public void DynamicExpressionParser_ParseLambda_Issue58()
         {
             var expressionParams = new[]
             {
@@ -1251,14 +1251,16 @@ public void DynamicExpressionParser_ParseLambda_Operator_Less_Greater_With_Guids
         }
 
         [Theory]
-        [InlineData("c => c.Age == 8", "c => (c.Age == 8)")]
-        [InlineData("c => c.Name == \"test\"", "c => (c.Name == \"test\")")]
-        public void DynamicExpressionParser_ParseLambda_RenameParameterExpression(string expressionAsString, string expected)
+        [InlineData(true, "c => c.Age == 8", "c => (c.Age == 8)")]
+        [InlineData(true, "c => c.Name == \"test\"", "c => (c.Name == \"test\")")]
+        [InlineData(false, "c => c.Age == 8", "Param_0 => (Param_0.Age == 8)")]
+        [InlineData(false, "c => c.Name == \"test\"", "Param_0 => (Param_0.Name == \"test\")")]
+        public void DynamicExpressionParser_ParseLambda_RenameParameterExpression(bool renameParameterExpression, string expressionAsString, string expected)
         {
             // Arrange
             var config = new ParsingConfig
             {
-                RenameParameterExpression = true
+                RenameParameterExpression = renameParameterExpression
             };
 
             // Act
@@ -1500,22 +1502,28 @@ public void DynamicExpressionParser_ParseLambda_Func()
         }
 
         [Theory]
-        [InlineData(1, true)]
-        [InlineData(5, false)]
-        public void DynamicExpressionParser_ParseLambda_Func2(int? input, bool expected)
+        [InlineData("value", "value != null && value == 1", 1, true)]
+        [InlineData("value", "value != null && value == 1", 5, false)]
+        [InlineData("x", "value != null && value == 1", 1, true)]
+        [InlineData("x", "value != null && value == 1", 5, false)]
+        [InlineData(null, "value != null && value == 1", 1, true)]
+        [InlineData(null, "value != null && value == 1", 5, false)]
+        [InlineData("value", "value => value != null && value == 1", 1, true)]
+        [InlineData("value", "value => value != null && value == 1", 5, false)]
+        public void DynamicExpressionParser_ParseLambda_Func2(string? paramName, string test, int? input, bool expected)
         {
             // Arrange
             var nullableType = typeof(int?);
-            var functionType = typeof(Func<,>).MakeGenericType(nullableType, typeof(bool));
-            var valueParameter = Expression.Parameter(nullableType, "value");
+            var delegateType = typeof(Func<,>).MakeGenericType(nullableType, typeof(bool));
+            var valueParameter = paramName is not null ? Expression.Parameter(nullableType, paramName) : Expression.Parameter(nullableType);
 
             // Act 1
             var expression = DynamicExpressionParser.ParseLambda(
-                functionType,
+                delegateType,
                 new ParsingConfig(),
                 new[] { valueParameter },
                 typeof(bool),
-                "value != null && value == 1"
+                test
             );
 
             // Act 2